Netflix网关zuul(1.x和2.x)全解析

zuul 是netflix开源的一个API Gateway 服务器, 本质上是一个web servlet应用。

Zuul可以通过加载动态过滤机制，从而实现以下各项功能：

• 验证与安全保障: 识别面向各类资源的验证要求并拒绝那些与要求不符的请求。
• 审查与监控: 在边缘位置追踪有意义数据及统计结果，从而为我们带来准确的生产状态结论。
• 动态路由: 以动态方式根据需要将请求路由至不同后端集群处。
• 压力测试: 逐渐增加指向集群的负载流量，从而计算性能水平。
• 负载分配: 为每一种负载类型分配对应容量，并弃用超出限定值的请求。
• 静态响应处理: 在边缘位置直接建立部分响应，从而避免其流入内部集群。
• 多区域弹性: 跨越AWS区域进行请求路由，旨在实现ELB使用多样化并保证边缘位置与使用者尽可能接近。

网关zuul从1.0到2.0 经历了较大的变化，先从架构上看看吧

 zuul 1.0的架构

 

从上图看，

1.ZuulServlet负责接收请求，对filter进行处理

/**
* Core Zuul servlet which intializes and orchestrates zuulFilter execution
*
* @author Mikey Cohen
*         Date: 12/23/11
*         Time: 10:44 AM
*/
@Override
public void service(javax.servlet.ServletRequest servletRequest, javax.servlet.ServletResponse servletResponse) throws ServletException, IOException {
try {
init((HttpServletRequest) servletRequest, (HttpServletResponse) servletResponse);

// Marks this request as having passed through the "Zuul engine", as opposed to servlets
// explicitly bound in web.xml, for which requests will not have the same data attached
RequestContext context = RequestContext.getCurrentContext();
context.setZuulEngineRan();

try {
preRoute();
} catch (ZuulException e) {
error(e);
postRoute();
return;
}
try {
route();
} catch (ZuulException e) {
error(e);
postRoute();
return;
}
try {
postRoute();
} catch (ZuulException e) {
error(e);
return;
}

} catch (Throwable e) {
error(new ZuulException(e, 500, "UNHANDLED_EXCEPTION_" + e.getClass().getName()));
} finally {
RequestContext.getCurrentContext().unset();
}
}

其中

FilterProcessor处理核心类

前置filter

runFilters("pre"); //前置filter类型

跳转filter

runFilters("route");

后置filter

runFilters("post");

2. zuul的核心是一系列的filters, 其作用可以类比Servlet框架的Filter，或者AOP。工作原理如下图所示

Zuul可以对Groovy过滤器进行动态的加载，编译，运行。FilterFileManager.java

/**
* This class manages the directory polling for changes and new Groovy filters.
* Polling interval and directories are specified in the initialization of the class, and a poller will check
* for changes and additions.
*
* @author Mikey Cohen
*         Date: 12/7/11
*         Time: 12:09 PM
*/
void processGroovyFiles(List<File> aFiles) throws Exception {

List<Callable<Boolean>> tasks = new ArrayList<>();
for (File file : aFiles) {
tasks.add(() -> {
try {
return filterLoader.putFilter(file);
}
catch(Exception e) {
LOG.error("Error loading groovy filter from disk! file = " + String.valueOf(file), e);
return false;
}
});
}
processFilesService.invokeAll(tasks, FILE_PROCESSOR_TASKS_TIMEOUT_SECS.get(), TimeUnit.SECONDS);
}

 3.对groovy文件的动态操作管理类FilterScriptManagerServlet

/**
* Servlet for uploading/downloading/managing scripts.
* <p/>
* <ul>
* <li>Upload scripts to the registry for a given endpoint.</li>
* <li>Download scripts from the registry</li>
* <li>List all revisions of scripts for a given endpoint.</li>
* <li>Mark a particular script revision as active for production.</li>
* </ul>
*/
@Override
protected void doPut(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

if (!adminEnabled.get()) {
response.sendError(HttpServletResponse.SC_FORBIDDEN, "Filter admin is disabled. See the zuul.filters.admin.enabled FastProperty.");
return;
}

// retrieve arguments and validate
String action = request.getParameter("action");
/* validate the action and method */
if (!isValidAction(request, response)) {
return;
}

// perform action
if ("UPLOAD".equals(action)) {
handleUploadAction(request, response);
} else if ("ACTIVATE".equals(action)) {
handleActivateAction(request, response);
} else if ("CANARY".equals(action)) {
handleCanaryAction(request, response);
} else if ("DEACTIVATE".equals(action)) {
handledeActivateAction(request, response);
}

}

zuul 2.0架构

 

从上图可以看到：

1.Zuul引入了Netty和RxJava，正如之前的 

ZuulFilter

 分为了 

Pre

,

Post

,

Route

,

Error

，Zuul2的Filter分为三种类型

• Inbound Filters: 在路由之前执行
• Endpoint Filters: 路由操作
• Outbound Filters: 得到相应数据之后执行

使用RxJava重写了

Pre

,

Post

,

Route Zuul

Filter的结构如下

 

ZuulServerChannelInitializer.java

@Override
protected void initChannel(Channel ch) throws Exception
{
// Configure our pipeline of ChannelHandlerS.
ChannelPipeline pipeline = ch.pipeline();

storeChannel(ch);
addTimeoutHandlers(pipeline);
addPassportHandler(pipeline);
addTcpRelatedHandlers(pipeline);
addHttp1Handlers(pipeline);
addHttpRelatedHandlers(pipeline);
addZuulHandlers(pipeline);
}

其父类实现了addZuulHandlers方法

protected void addZuulHandlers(final ChannelPipeline pipeline)
{
pipeline.addLast("logger", nettyLogger);
pipeline.addLast(new ClientRequestReceiver(sessionContextDecorator));
pipeline.addLast(passportLoggingHandler);
addZuulFilterChainHandler(pipeline);
pipeline.addLast(new ClientResponseWriter(requestCompleteHandler, registry));
}

protected void addZuulFilterChainHandler(final ChannelPipeline pipeline) {
final ZuulFilter<HttpResponseMessage, HttpResponseMessage>[] responseFilters = getFilters(   //1
new OutboundPassportStampingFilter(FILTERS_OUTBOUND_START),
new OutboundPassportStampingFilter(FILTERS_OUTBOUND_END));

// response filter chain
final ZuulFilterChainRunner<HttpResponseMessage> responseFilterChain = getFilterChainRunner(responseFilters,
filterUsageNotifier);

// endpoint | response filter chain
final FilterRunner<HttpRequestMessage, HttpResponseMessage> endPoint = getEndpointRunner(responseFilterChain,  //2
filterUsageNotifier, filterLoader);

final ZuulFilter<HttpRequestMessage, HttpRequestMessage>[] requestFilters = getFilters(                   //3
new InboundPassportStampingFilter(FILTERS_INBOUND_START),
new InboundPassportStampingFilter(FILTERS_INBOUND_END));

// request filter chain | end point | response filter chain
final ZuulFilterChainRunner<HttpRequestMessage> requestFilterChain = getFilterChainRunner(requestFilters,
filterUsageNotifier, endPoint);

pipeline.addLast(new ZuulFilterChainHandler(requestFilterChain, responseFilterChain));
}

调用Handler处理

@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
if (msg instanceof HttpRequestMessage) {
zuulRequest = (HttpRequestMessage)msg;

//Replace NETTY_SERVER_CHANNEL_HANDLER_CONTEXT in SessionContext
final SessionContext zuulCtx = zuulRequest.getContext();
zuulCtx.put(NETTY_SERVER_CHANNEL_HANDLER_CONTEXT, ctx);
zuulCtx.put(ZUUL_FILTER_CHAIN, requestFilterChain);

requestFilterChain.filter(zuulRequest);
}
else if ((msg instanceof HttpContent)&&(zuulRequest != null)) {
requestFilterChain.filter(zuulRequest, (HttpContent) msg);
}
else {
LOG.debug("Received unrecognized message type. " + msg.getClass().getName());
ReferenceCountUtil.release(msg);
}
}

调用ZuulFilterChainRunner的filter方法

@Override
public void filter(T inMesg, HttpContent chunk) {
String filterName = "-";
try {
Preconditions.checkNotNull(inMesg, "input message");

final AtomicInteger runningFilterIdx = getRunningFilterIndex(inMesg);
final int limit = runningFilterIdx.get();
for (int i = 0; i < limit; i++) {
final ZuulFilter<T, T> filter = filters[i];
filterName = filter.filterName();
if ((! filter.isDisabled()) && (! shouldSkipFilter(inMesg, filter))) {
final HttpContent newChunk = filter.processContentChunk(inMesg, chunk);
if (newChunk == null)  {
//Filter wants to break the chain and stop propagating this chunk any further
return;
}
//deallocate original chunk if necessary
if ((newChunk != chunk) && (chunk.refCnt() > 0)) {
chunk.release(chunk.refCnt());
}
chunk = newChunk;
}
}

if (limit >= filters.length) {
//Filter chain has run to end, pass down the channel pipeline
invokeNextStage(inMesg, chunk);
} else {
inMesg.bufferBodyContents(chunk);

boolean isAwaitingBody = isFilterAwaitingBody(inMesg);

// Record passport states for start and end of buffering bodies.
if (isAwaitingBody) {
CurrentPassport passport = CurrentPassport.fromSessionContext(inMesg.getContext());
if (inMesg.hasCompleteBody()) {
if (inMesg instanceof HttpRequestMessage) {
passport.addIfNotAlready(PassportState.FILTERS_INBOUND_BUF_END);
} else if (inMesg instanceof HttpResponseMessage) {
passport.addIfNotAlready(PassportState.FILTERS_OUTBOUND_BUF_END);
}
}
else {
if (inMesg instanceof HttpRequestMessage) {
passport.addIfNotAlready(PassportState.FILTERS_INBOUND_BUF_START);
} else if (inMesg instanceof HttpResponseMessage) {
passport.addIfNotAlready(PassportState.FILTERS_OUTBOUND_BUF_START);
}
}
}

if (isAwaitingBody && inMesg.hasCompleteBody()) {
//whole body has arrived, resume filter chain
runFilters(inMesg, runningFilterIdx);
}
}
}
catch (Exception ex) {
handleException(inMesg, filterName, ex);
}
}

2.NettyClient 

if (filter.getSyncType() == FilterSyncType.SYNC) {
final SyncZuulFilter<I, O> syncFilter = (SyncZuulFilter) filter;
final O outMesg = syncFilter.apply(inMesg);
recordFilterCompletion(SUCCESS, filter, startTime, inMesg, snapshot);
return (outMesg != null) ? outMesg : filter.getDefaultOutput(inMesg);
}

// async filter
filter.incrementConcurrency();
resumer = new FilterChainResumer(inMesg, filter, snapshot, startTime);
filter.applyAsync(inMesg)
.observeOn(Schedulers.from(getChannelHandlerContext(inMesg).executor()))
.doOnUnsubscribe(resumer::decrementConcurrency)
.subscribe(resumer);

ProxyEndpoint.java

@Override
public HttpResponseMessage apply(final HttpRequestMessage input) {
// If no Origin has been selected, then just return a 404 static response.
// handle any exception here
try {

if (origin == null) {
handleNoOriginSelected();
return null;
}

origin.getProxyTiming(zuulRequest).start();

// To act the same as Ribbon, we must do this before starting execution (as well as before each attempt).
IClientConfig requestConfig = origin.getExecutionContext(zuulRequest).getRequestConfig();
originalReadTimeout = requestConfig.getProperty(ReadTimeout, null);
setReadTimeoutOnContext(requestConfig, 1);

origin.onRequestExecutionStart(zuulRequest);
proxyRequestToOrigin();

//Doesn't return origin response to caller, calls invokeNext() internally in response filter chain
return null;
} catch (Exception ex) {
handleError(ex);
return null;
}
}

将请求转发至远端

private void proxyRequestToOrigin() {
Promise<PooledConnection> promise = null;
try {
attemptNum += 1;
requestStat = createRequestStat();
origin.preRequestChecks(zuulRequest);
concurrentReqCount++;

// update RPS trackers
updateOriginRpsTrackers(origin, attemptNum);

// We pass this AtomicReference<Server> here and the origin impl will assign the chosen server to it.
promise = origin.connectToOrigin(zuulRequest, channelCtx.channel().eventLoop(), attemptNum, passport, chosenServer, chosenHostAddr);

storeAndLogOriginRequestInfo();
currentRequestAttempt = origin.newRequestAttempt(chosenServer.get(), context, attemptNum);
requestAttempts.add(currentRequestAttempt);
passport.add(PassportState.ORIGIN_CONN_ACQUIRE_START);

if (promise.isDone()) {
operationComplete(promise);
} else {
promise.addListener(this);
}
}
catch (Exception ex) {
LOG.error("Error while connecting to origin, UUID {} " + context.getUUID(), ex);
storeAndLogOriginRequestInfo();
if (promise != null && ! promise.isDone()) {
promise.setFailure(ex);
} else {
errorFromOrigin(ex);
}
}
}

调用BasicNettyOrigin

@Override
public Promise<PooledConnection> connectToOrigin(HttpRequestMessage zuulReq, EventLoop eventLoop, int attemptNumber,
CurrentPassport passport, AtomicReference<Server> chosenServer,
AtomicReference<String> chosenHostAddr) {
return clientChannelManager.acquire(eventLoop, null, zuulReq.getMethod().toUpperCase(),
zuulReq.getPath(), attemptNumber, passport, chosenServer, chosenHostAddr);
}

 

3.小结

   >> zuul2通过启动BaseServerStartup的实现类，启动一个netty server

   >> netty server将ZuulFilter (

Inbound

, 

Outbound

, 

EndPoint)包裹成ChainRunner组合成netty的一个handler：ZuulFilterChainHandler

   >> ZuulFilterChainHandler将请求包装成SyncZuulFilter封装成NettyClient

4.zuul1和zuul2的选择

  性能对比

Zuul 1 (阻塞)的应用场景

  cpu密集型任务

  简单操作的需求

  开发简单的需求

  实时请求高的

zuul2(非阻塞)的应用场景

  io密集的任务

  大请求或者大文件

  队列的流式数据

  超大量的连接

参考文献

【1】https://www.cnblogs.com/lexiaofei/p/7080257.html

【2】https://blog.csdn.net/lengyue309/article/details/82192118

【】https://github.com/strangeloop/StrangeLoop2017/blob/master/slides/ArthurGonigberg-ZuulsJourneyToNonBlocking.pdf